Apparatus for pulverizing coal and like substances



Nov. 11,1930. w, DRUMMOND 1,781,572

APPARATUS FOR PULVERIZING COAL AND LIKE SUBSTANCES Filed Jan. 4, 1950 2 Sheets-Sheet 1 wa /W Nov. 11, 1930. w. J. DRUMMOND 1,781,572

APPARATUS FOR PULVERIZING COAL AND LIKE SUBSTANCES Filed Jan. 4, 1930 2 Sheets-Sheet 2 Patented Nov. 11, 1930 UNITE ES WALTER JAMES DRUMMOND, OF NEWCASTLE-UPON-TYNE, ENGLAND, ASSIGNOR OF ONE-HALF TO ASHINGTON' COAL COMPANY LIMITED, OF NEWCASTLE-UPON-TYNE, ENGLAND, A COMPANY, OF GREAT BRITAIN APPARATUS FOR PULVERIZING COAL AND LIKE SUBSTANCES Application filed January 4, 1930, Serial No.

This invention relates to apparatusfor pulverizing coal andlike substances, of the kind in which the finely divided particleswhich constitute the finished'product are remo'vedfrom the grinding zone by means of a current of air.

The object of this invention is to prevent the accumulation in the grinding zone of iron pyritesand other heavy particles which damage the grinding members and at present necessitate frequent interruption of the working machine while such particles are removed;

According to this invention a number of receptacles is'p'rovided, each communicating with the grinding zone through openings preferably formed at the'outside of the track where the heavier particles at presenttend to accumulate, and means are provided for admitting air into each receptacle to sweep back any lighterparticles-which tend to fall into the receptacle. Each receptacle has a discharge opening normally closed by a flap or cover which is automatically opened when the receptacle contains a predetermined charge. These-covers may be positively actuated or they may be controlled'by means'of a spring or Weight adapted to open automatically to-disoha'rge the contents of the receptacles when a predetermined amount has accumulated;

The invention is particularly applicable to the type of mill in which the material to be ground isploughed up into-the grinding zone from which the finished product in the form of fine particles is separated from the coarser materials by means of a current'o'f air constantly sweeping through the mill, and one arrangement according. to the present invention together with certain modifications as applied to such a mill is illustrated somewhat diagrammatically in the'accompany ing drawings, in which:

Figure l isasection'al side elevation showing the grinding mechanism but omitting portions which form no part of the invention,

Figure 2 is a section of a portion of the apparatus as shown in Figure on an enlarged scale;

418,595, and in Great Britain April 24, 1929.

Figure 3 is a plan on the line 3-3 of F igure 2, and

Figures 4 and 5 show in side elevation modified forms of collecting receptacles.

In the apparatus illustrated in Figures 1,

2 and 3 grinding rollers A are carried on spindles A rotatable within frames A pivotally mounted at A on the ends of a crosshead B which is keyed to a shaft B rotatable through gearing B by a main driving shaft B. Secured to the crosshead B is a sleeve C carrying at its lower end a series of'ploughs one of which is shown at C which are so arranged that they terminate just above a stationary table D.- When the main driving shaft B is rotated, the rollers A tend to swing outwards on the pivots A under centrifugal action so as to bear against a grinding ring E. The material to be ground is introduced through a hopper'F provided at one side of the main casing F, and on passing down into the mill is pulverized between the rollers A and the ring E. At the same time the ploughs C are moved in a circular path over the table D and lift the material which has passed between the grinding elements back into the'grindin zone. The fine particles, i. e. that part 0 the ma terial which has been fully ground, is separated from the coarser material by means of a current of air which enters the mill through one or moreair ports G, being then deflected by vanes G (Figure 3) so as to whirl over the table D and carry the lighter particles out of the grinding zone and through the upper end of the casing F as indicated by the arrows in Figure 1. The material heavier than the bulk to be ground, such for example as metallic impurities, tends to accumulate at the outer periphery of the table D under the combined influence of centrifugal force and gravity, and according to the present invention openings H (Figure 3) are provided at suitable intervals, preferably outside the plough track as shown, where the heavier particles at present tend to accumulate.

The openings H open into a circular chan? nel H formed near the periphery of the table each passage leading to a collecting receptacle'J (clear y'showniu Figurc 2). Ea h receptacle has a nozzle J and a discharge outlet J 2 which is normally closed by means of a fiap or door J controlled mechanically or by an adjustable counterweight- J as shown and provided with inlet ports J 5 which can be controlled or adjusted by means of a perforated ring J The depression caused within the mill by the air current entering by the ports G will result in a. current of air passing through the ports J and the amount of this air admitted can be so controlled that while the heavier particles which fall into the receptacles J accumulate there, any lighter particles also carried into the receptacles are swept back into the mill. When any of the receptacles J contains a predetermined charge of heavy particles, the door J 3 opens and the contents of the receptacle are discharged. If desired, the counterweight J 4 may be replaced by a spring.

A slightly modified form of receptacle is shown in Figure 4 and comprises a cylindrical nozzle K having ports K and an externally threaded portion K on which an internally threaded ring K is mounted which ggn be turned to cover or uncover the ports Figure 5 illustrates another alternative form of receptacle in which a door L is periodically opened by means of a solenoid L controlled by a suitable timing mechanism (not shown) adapted to open and close the door L at predetermined intervals.

If the grinding mill is of the kind in which the depression in the grinding chamber is insufiicient to produce the necessary current of air through the receptacle or inlet nozzle to separate the lighter particles from the heavier particles, means may be provided for introducing air into the receptacles at an increased pressure so as to effect the desired separation between the particles to be accumulated and those which are to be returned to the grinding zone. For example an air pipe M (Figure 5) may be arranged to supply air at increased pressure to ports M provided in the upper part of the receptacle.

It will be appreciated that the constructions above described are given by way of example only and that details may be modified considerably in accordance with the type of mill employed and the material under treatment without departing from this invention. Further, the application of the in v-ention is not to be confined to mills of the type above described but is applicable to all mills of the type which depend on air separation for the removal of the ground product.

What I claim is my invention and desire to secure by Letters Patent is 1. In apparatus for pulverizing coal and like substances the combination of a grind ing chamber having an inlet for unground material and an outlet through which the fine ground particles are discharged by means of an air current, receptacles communicating with the grinding chamber within which receptacles the heavier particles tend to accumulate, and means for admitting a current of air into each receptacle and thus driving back into the grinding chamber any lighter particles which have been carried into the receptacles.

2. In apparatus for pulverizing coal and like substances the combination of a grinding chamber having an inlet for unground material and an outlet through which the fine ground particles are discharged by means of an air current, receptacles communicating with the grinding chamber Within which receptacles the heavier particles tend to accumulate, means for admitting a current of air into each receptacle and thus driving back into the grinding chamber any lighter particles which have been carried into the receptacles, and means for periodically discharging the heavier particles accumulated in each receptacle.

3. In apparatus for pulverizing coal and like substances the combination of a grinding chamber having an inlet for unground material and an outlet through which the fine ground particles are discharged by means of an air current, of a plurality of receptacles communicating with the track of the grinding chamber into which receptacles the heavier particles fall and tend to accumulate, means for admitting a current of air into each receptacle and thus returning to the grinding zone any lighter particles which may have been carried into the receptacle, and means for automatically discharging the heavier particles in each receptacle.

4. In apparatus for pulverizing coal and like substances the combination of a grinding chamber having an inlet for unground material and an outlet through which the fine particles are discharged by means of an air current, a plurality of receptacles communicating with the track of the grinding chamber in which receptacles the heavier particles accumulate, each receptacle comprising a nozzle communicating with the grinding chamber and having adjustable air inlet ports furnished with a discharge door which is normally closed but adapted to open automatically so as periodically to discharge the heavier particles accumulated in the receptacle.

5. In apparatus for pulverizing coal and like substances the combination of a grinding chamber having an inlet for unground material and an outlet through which the fine particles are discharged by means of an air current, a plurality of receptacles communicating with the track of the grinding chamber in which receptacles the heavier particles accumulate, each receptacle comprising a nozzle communicating with. the

grinding chamber having adjustable air inlet ports and furnished with a discharge door, and means for positively operating the said door to empty the heavier particles from the receptacle.

In testimony whereof I have signed my name to this specification.

WALTER JAMES DRUMMOND. 

